refactor: simplify MainApp for .NET 8 DPI handling

DPI awareness is now handled by the ApplicationHighDpiMode project property.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest/MainApp.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Runtime.InteropServices;
+using System;
 using System.Windows.Forms;
 using OpenNest.Forms;
 
@@ -7,21 +6,12 @@ namespace OpenNest
 {
     internal static class MainApp
     {
-        /// <summary>
-        /// The main entry point for the application.
-        /// </summary>
         [STAThread]
         private static void Main()
         {
-            if (Environment.OSVersion.Version.Major >= 6)
-                SetProcessDPIAware();
-
             Application.EnableVisualStyles();
             Application.SetCompatibleTextRenderingDefault(false);
             Application.Run(new MainForm());
         }
-
-        [DllImport("user32.dll")]
-        private static extern bool SetProcessDPIAware();
     }
 }